Electric motor having a thermal fuse

ABSTRACT

An electric motor for driving a motor vehicle component, particularly a fan wheel for cooling coolant water, contains a rotor that is rotatably mounted opposite a stator, and an electronic system. The electronic system contains a punched grid provided with a plastic over-mold and a current path which conducts the motor current and has two current path ends spaced apart from one another forming an interruption point that is bridged by a thermal fuse. The thermal fuse has a spring-loaded contact bridge which is held so as to pivot about an axis that extends perpendicularly to the plane in which the interruption point lies.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation application, under 35 U.S.C. §120, of copendinginternational application No. PCT/EP2013/076638, filed Dec. 16, 2013,which designated the United States; this application also claims thepriority, under 35 U.S.C. §119, of German patent application Nos. DE 102012 024 604.8, filed Dec. 15, 2012, and DE 10 2013 002 155.3, filedFeb. 7, 2013; the prior applications are herewith incorporated byreference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to an electric motor, in particular a brushlesselectric motor, for driving a motor vehicle component. The electricmotor contains a rotor mounted rotatably relative to a stator and anelectronics system, which has a punched grid provided with a plasticover-mold and a current path which conducts the motor current and hastwo current path ends spaced apart from one another forming aninterruption point that is bridged by a thermal fuse. The thermal fusehas a spring-loaded contact bridge. In particular, a vehicle componentis understood to be a fan wheel for cooling coolant water.

German utility model DE 20 2010 002 664 U1 discloses an electric motor,in particular a DC motor, for driving a motor vehicle component,particularly a fan motor for cooling coolant water, having a rotor and acommutator, against which a brush bears with contact. A punched gridover-molded with plastic forms a current path impressed into anelectrical isolation, the current path being connected to a brush. Thecurrent path, which conducts the motor current, is interrupted so as toform two current path ends spaced apart from one another, and theinterruption point is bridged by a contact spring as thermal fuse.

German patent DE 10 2009 036 578 B3 relates to a thermal fuse, inparticular for a power module of a motor vehicle. The thermal fuse has aconductive path, which is arranged on a circuit board and is interruptedby an interruption point, and which has a first conductive path portionand a second conductive path portion in each case adjacent to theinterruption point. A contact bridge, which is arranged in the region ofthe interruption point, has a first contact portion and a second contactportion arranged opposite one another. The contact portions are securedin a first position to the conductive path portions by solder atsoldered points. The contact bridge is acted on in the first contactposition by a spring force, in such a way that the contact portions areseparated from the corresponding conductive path portions when themelting point of the solder is reached. The thermal fuse also has aspring element, which, when the melting point of the solder is reached,causes a movement of the contact bridge, which extends parallel to thecircuit board. In the second or tripped position the contact bridge isheld in a cage without contacting the first conductive path portion.

SUMMARY OF THE INVENTION

The object of the invention is to specify an electric motor, inparticular a brushless electric motor, for driving a motor vehiclecomponent, particularly a fan wheel for cooling coolant water containinga thermal fuse, which on the one hand requires a low component partoutlay, and with which on the other hand a simple and/or effectivearrangement of the component parts in the manufacturing process isenabled.

For this purpose, the electric motor has a rotor that is mountedrotatably relative to a stator, an electronics system with a punchedgrid provided with a plastic over-mold having a current path whichconducts the motor current. The current path has two current path endsspaced apart from one another forming an interruption point. A thermalfuse has a spring-loaded contact bridge for bridging the interruptionpoint, wherein the contact bridge is held pivotably about an axis thatextends perpendicularly to the plane in which the interruption pointlies.

In an advantageous embodiment of the electric motor the contact bridgepivots about the pivot axis in the plane of the interruption point. Apossibility for the space-saving arrangement of the thermal fuseinclusive of the contact bridge and of the spring element and contactbridge is thus made possible.

In accordance with an expedient development the contact bridge isassociated with a separate spring element having a first spring leg andhaving a second spring leg extending at least approximately at rightangles hereto. A structurally simple and particularly effective springelement can thus be provided and placed in the arrangement.

In accordance with a preferred variant the spring legs transition intoone another via a spring or leg eyelet, which in particular is open. Thespring can thus be arranged pivotably in an axis on a shaft element, forexample a pin or the like, and a favorable configuration of the springcan be produced. In the assembled state the spring eyelet of the springelement surrounds the pivot axis coaxially. A joint pivoting of thespring element, or spring leg thereof cooperating with the contactbridge, and the contact bridge about the same pivot axis is thusprovided easily and also reliably.

In a further favorable embodiment the first spring leg lies in a storagecompartment of the plastic over-mold, whereas the second spring legbears against the contact bridge under a spring preload. In the startingstate the spring legs of the spring element are arranged relative to oneanother at a suitable angle, such that in the installed state the springlegs are preferably arranged perpendicularly to one another when thesecond spring leg bears against the contact bridge. The preload of thecontact bridge by the spring element is thus produced in a simple andalso reliable manner. The separate spring element is suitably fabricatedfrom round wire or flat wire in the manner of a leg spring. Aneconomical possibility is thus provided for producing the springelement.

In accordance with an expedient development the spring element and thecontact bridge are coupled via a guide element. The contact bridge isthus guided reliably while it passes through the pivot path. For thispurpose, the guide element is suitably formed by a groove in the firstspring leg and a spring on the contact bridge. A favorable and practicalimplementation of the spring element is thus provided, which alsoenables simple handling with regard to the assembly of the componentparts.

In accordance with a suitable embodiment the first spring leg of thespring element is bent at the leg end. A stable hold of the springelement on the contact bridge is thus provided.

In a further advantageous embodiment the pivot axis is shaped in theform of a pin from the plastic over-mold. As a result of this structure,the possibility is created that the spring element, in contrast to thecontact bridge, itself is not an active component of the thermal fuse oris only insignificantly an active component of the thermal fuse, suchthat an electrical current flow is provided only via the contact bridge.The current flow therefore is not influenced by the mechanicalproperties of the contact bridge.

The contact bridge advantageously has, at both ends, contact surfacescontacted with the respective current path ends, wherein the pivot axislies in the region of the contact surfaces. The possibility is thuscreated of bridging the interruption point for conduction, soldering thecontact bridge at the current path ends, and at the same time alsoproducing the pivotability of the contact bridge.

Both contact surfaces of the contact bridge are suitably soldered to thecurrent path ends. On the one hand a particularly reliable electricaltransfer capability of the current via the contact bridge is thusprovided. On the other hand the contact bridge is fixed to the currentpath ends mechanically reliably. In the case of overheating the solderin the region of both current path ends melts practically at the sametime, such that the contact bridge in the event of tripping can bepivoted out about the pivot axis and in the plane of the interruptionpoint. The melted solder joints are practically sheared off during thisprocess, which ensures a reliable interruption of the interruption orcontact point bridged by the thermal fuse or contact bridge thereof.

In an expedient variant the contact bridge is configured as, or in themanner of a punched and bent part having a number of bends, which form amiddle raised bridge portion. The desired mechanical and/or electricalproperties of the contact bridge can thus be provided in a simplemanner. In particular, the contact bridge can be adapted to differentamperages.

The advantages associated with the invention in particular lie in thefact that a simple, favorable and space-saving possibility forintegration of the thermal fuse in the electric motor is created by atripping of the thermal fuse in the plane of the interruption point.

Other features which are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin an electric motor having a thermal fuse, it is nevertheless notintended to be limited to the details shown, since various modificationsand structural changes may be made therein without departing from thespirit of the invention and within the scope and range of equivalents ofthe claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a diagrammatic, exploded perspective view of a cooler fan fora motor vehicle with a brushless internal rotor motor with integratedconverter electronics system according to the invention;

FIG. 2 is a perspective view of an electronics compartment with anelectronics system of an electric motor, with a printed circuit boardand a punched grid provided with a plastic over-mold, and with a thermalfuse;

FIGS. 3A and 3B are perspective views of a punched grid before and afterthe plastic over-mold inclusive of an interruption point to be bridgedby the thermal fuse;

FIG. 4 is a perspective view of a detail of the electronics system withthe thermal fuse; and

FIGS. 5A to 5C are top plan views showing the thermal fuse with aspring-loaded contact bridge in a contact position, in a pivotedposition and in a tripped position.

DETAILED DESCRIPTION OF THE INVENTION

Parts corresponding to one another are provided in all figures with thesame reference signs.

Referring now to the figures of the drawings in detail and first,particularly to FIG. 1 thereof, there is shown a fan 1 for a radiator ofa motor vehicle in a state removed from one another. The fan 1 includesa fan wheel 2 with a central cap 3, around an outer circumference ofwhich air-guiding blades 4 (illustrated only in part) are arranged in anevenly distributed manner. The fan 1 also has an electric motor 5, alsoreferred to as a fan motor, by which the fan wheel 2 is driven inrotation.

The motor 5 is formed generally by a stator 6, which is wound with athree-phase rotary field winding 7 in the form of coils. The motor 5also includes a permanently excited rotor 8, which is mounted rotatablyabout a motor axis 9 in an interior of the stator 6. In order to mountthe rotor 8, the motor 5 has two rolling bearings 10 and 11, which acton the rotor 8 from axially opposite sides. The axial play of the rotor8 between the two rolling bearings 10 and 11 is spring-loaded here by aspring ring 12.

The motor 5 also has an approximately disk-shaped motor mount 13. Anelectronics compartment 14 is formed in the motor mount 13 on an endface facing away from the fan wheel 2, a converter electronics system 15being inserted into the electronics compartment 14. In order to tightlyclose the electronics compartment 14, the motor 5 contains anelectronics compartment lid 16, also referred to hereinafter as ahousing lid.

The rotor 8 is formed (in a manner not illustrated in greater detail) bya laminated core, into which permanent magnets are inserted in order togenerate an exciting field, wherein the laminated core together with theinserted permanent magnets is over-molded by a plastic coating.Similarly, the stator 6 also consists of a laminated core that isover-molded by a plastic coating.

The motor mount 13 is formed in particular by a one-piece die-cast partmade of aluminum. The electronics compartment lid 16 is preferably aninjection molded part made of plastic.

On the front side thereof, the rotor 8 is provided with four screw domes18, by which the rotor 8 is screwed to the fan wheel 2 in the assembledstate. The motor 5 and therefore the entire fan 1 is secured to thevehicle via the motor mount 13, which for this purpose is provided withthree screw tabs 19 protruding from the outer circumference of themount. The motor 5 is a brushless, self-cooled internal rotor motor.

FIG. 2 shows a perspective illustration of the electronics compartment14 with inserted electronics system 15. The electronic system 15 has anover-molded punched grid 20 and a circuit board or printed circuit board21 fitted with electrical component parts. The electric motor 5 isoperated by a bridge circuit (B6 circuit), which is implemented in theover-molded punched grid 20. For this purpose the over-molded punchedgrid 20 has a number of switchable semiconductor components 22, by whichcurrent is supplied alternately to the three phase windings of the fieldwinding 7 of the electric motor 5. The electrical current used for thispurpose is provided by a DC source in a manner not illustrated ingreater detail.

The three phase windings of the field winding 7 of the electric motor 5are connected for example in a delta connection via capacitors 23. Inother words each two electrically adjacent phase windings areelectrically connected to one another at a motor-side contact point andin each case are in turn electrically contacted via a bridge-sidecontact point to a bridge branch of the bridge circuit. The windings areproduced from a lacquered copper wire and are wound centrally to form acoil.

The over-molded punched grid 20, additionally to the semiconductorcomponents 22 and the capacitors 23, also has a thermal fuse 24. Thethermal fuse 24 protects the electric motor 5 against overheating andfire risk. If the motor 5 overheats, the thermal fuse 24 thus trips, andcurrent can no longer flow to or from the motor 5. Connections 25, 26and 27 form an input connection and an output connection for the motorcurrent and two sensor signal outputs, for example for the measurementsof the rotational speed (number of revolutions), the direction ofrotation and/or the position of the motor 5.

As is shown in FIG. 2 together with FIGS. 3A, 3B, the input connection25 is connected to the semiconductor components 22 via the capacitors23. A punched grid 28 (see FIG. 3A) provides conductive paths and iselectrically insulated by a plastic over-mold 29 (see FIG. 3B). Thepunched grid 28 or these conductive paths conducts/conduct the motorcurrent I_(M).

FIG. 4 shows the thermal fuse 24 in an enlarged illustration. Thethermal fuse 24 connects the current path ends 30, 31 conducting themotor current I_(M) to one another via an interruption point 32 of thepunched grid 28. The thermal fuse 24 is formed from a contact bridge 33,which connects two contact points 34, 35 of the punched grid 28 to oneanother. The contact bridge 33 itself has contact points 36 and 37,which are connected by a soldered joint to the contact points 34, 35 ofthe punched grid 28. The soldered points contact the current path ends30 and 31 to one another electrically via the contact bridge 33 andconnect the contact bridge 33 mechanically to the contact points 34 and35 to form a mechanically fixed connection.

In order to provide the function of the thermal fuse 24, a separatespring element 38 is provided, which preloads the contact bridge 33 by afirst spring leg 39 and is inserted in a storage compartment 41 of theplastic over-mold 29 by a second spring leg 40. The spring element 38 isdeformed in this position in such a way that the spring legs 39 and 40are arranged practically at right angles relative to one another. Bothspring legs 39 and 40 are interconnected via a leg eyelet 42.

The spring element 38 and the contact bridge 33 are also mountedrotatably about an axis 43, which is perpendicular to the plane in whichthe interruption point 32 lies. The axis 43 is formed from the over-mold29 as a rotary or pivot pin 44. Here, the leg eyelet 42 is arrangedcoaxially with respect to the pin 44 and thus with respect to the pivotaxis 43.

The contact bridge 33 is formed in the manner of a punched and bent parthaving a number of bends, which form a middle raised bridge portion. Thespring element 38 can be produced from round wire or also flat wire. Nocurrent flows via the spring element 38, since the pin 44 is formed fromthe insulating over-mold and the spring element 38 is fitted thereon.

The first spring leg 39 of the spring element 38 has a bend 45 at theleg end, which bend guides the contact bridge 33 in the event oftripping. In addition, the thermal fuse 24 also contains a guide element46 in the form of a groove/spring connection. Here, the spring element38 in the event of tripping guides the contact bridge 33 during thepivot over the pivot path thereof. The groove 46 a is formed here on thecontact bridge 33, and the spring 46 b is located on the first springleg 39 of the spring element 38.

On the basis of FIGS. 5A to 5C it is shown how, in the event of trippingonce the solder of the soldered points has melted, the contact bridge 33and also the spring element 38 pivot about the pin 44 and thus about theaxis. The pivot axis 43 lies here in the vicinity of the contact surface37. There, the contact bridge 33 has a bore, through which the pin 44 ispassed.

The thermal fuse 24 trips in particular in the event of anover-temperature, in that the solder melts and the contact bridge pivotsthrough a combined rotary and shearing movement on account of the springforce of the spring element 38, such that the interruption point 32bridged by the preloaded contact bridge 33 is interrupted. The contactbridge 33 pivots in the event of tripping from a first position (contactposition) into a second position (tripped position), wherein the pivotmovement is performed about the pivot axis 43 and in the plane of theinterruption point 32.

The invention is not limited to the above-described exemplaryembodiments. Rather, other variants of the invention can also be derivedherefrom by a person skilled in the art without departing from thesubject matter of the invention. In particular, all individual featuresdescribed in conjunction with the individual exemplary embodiments canalso be combined with one another in a different way without departingfrom the subject matter of the invention.

The following is a summary list of reference numerals and thecorresponding structure used in the above description of the invention:

-   1 fan-   2 fan wheel-   3 cap-   4 air-guiding blade-   5 fan/motor-   6 stator-   7 rotary field winding-   8 rotor-   9 motor axis-   10 rolling bearing-   11 rolling bearing-   12 spring ring-   13 motor mount-   14 electronics compartment-   15 converter/electronics-   16 electronics compartment lid-   17 axis pin-   18 screw dome-   19 end face-   20 overmolded punched grid-   21 printed circuit board-   22 semiconductor component-   23 capacitors-   24 thermal fuse-   25 input connection-   26 output connection-   27 sensor signal outputs-   28 punched grid-   29 plastic overmold-   30 first current path end-   31 second current path end-   32 interruption point-   33 contact bridge-   34 first contact point of the punched grid-   35 second contact point of the punched grid-   36 first contact point of the contact bridge-   37 second contact point of the contact bridge-   38 spring element-   39 first spring leg-   40 second spring leg-   41 receiving compartment of the plastic overmold-   42 leg/spring eyelet-   43 pivot axis-   44 pin-   45 bend-   46 guide element-   46 a groove-   46 b spring

1. An electric motor for driving a motor vehicle component, the electricmotor comprising: a stator; a rotor mounted rotatably relative to saidstator; and an electronics system having a plastic over-mold, a punchedgrid covered by said plastic over-mold and a current path conducting amotor current, said current path having a thermal fuse, two current pathends spaced apart from one another forming an interruption point beingbridged by said thermal fuse, said thermal fuse having a spring-loadedcontact bridge, said spring-loaded contact bridge being held pivotablyabout an axis extending perpendicularly to a plane in which saidinterruption point lies.
 2. The electric motor according to claim 1,wherein said spring-loaded contact bridge, when said thermal fuse trips,pivots in a manner of a combined rotary and shearing movement as aresult of a spring return force.
 3. The electric motor according toclaim 1, wherein said spring-loaded contact bridge has a spring elementwith a first spring leg and a second spring leg extending at leastapproximately at right angles to said first spring leg.
 4. The electricmotor according to claim 3, wherein said spring element has a springeyelet and said first and second spring legs transition into one anothervia said spring eyelet.
 5. The electric motor according to claim 3,wherein: said first spring leg bears against said spring-loaded contactbridge under a spring preload; and said plastic over-mold has a storagecompartment and said second spring leg lies in said storage compartmentof said plastic over-mold.
 6. The electric motor according to claim 3,wherein said spring element is fabricated from round wire or flat wire.7. The electric motor according to claim 3, wherein said thermal fusehas a guide element, said spring element and said spring-loaded contactbridge are coupled via said guide element.
 8. The electric motoraccording to claim 7, wherein said first spring leg has a groove formedtherein, said guide element is formed by said groove in said firstspring leg and a spring on said spring-loaded contact bridge.
 9. Theelectric motor according to claim 3, wherein said first spring leg has aleg end and is bent at said leg end.
 10. The electric motor according toclaim 1, wherein said pivot axis is formed from said plastic over-mold.11. The electric motor according to claim 1, wherein said spring-loadedcontact bridge has, at both ends, contact surfaces contacted with one ofsaid path ends, wherein said pivot axis lies in a region of one of saidcontact surfaces.
 12. The electric motor according to claim 11, whereinboth of said contact surfaces of said spring-loaded contact bridge aresoldered to said current path ends.
 13. The electric motor according toclaim 1, wherein said spring-loaded contact bridge is formed as, or in amanner of a punched and bent part having a number of bends forming amiddle raised bridge portion.
 14. The electric motor according to claim4, wherein in an assembled state of said spring element, said springeyelet surrounds said pivot axis coaxially.
 15. The electric motoraccording to claim 1, wherein the electric motor drives a fan wheel forcooling coolant water.